Identifying the important SNPs in the aging pathways requires the availability of suitable phenotype measures that properly reflect the process. The traditional focus of much aging research has been on survival, and especially on extreme longevity and centenarians. However, the reported heritability of lifespan is modest - 26% for males and 23% for females. Also, it is clear that environmental factors play a strong role in survival, as genetic factors cannot explain the extraordinary rise in human longevity experienced in recent decades. In contrast to survival, certain aspects of physical functioning, notably speed of walking and standing up from the sitting position, and muscle strength in old age, appear to be highly heritable. It has reported that the heritability of performance on an 8-foot walk in the National Heart, Lung, and Blood Institute (NHLBI) Twin Study was 51%, and time to rise from a chair five times was 56%. This work will try to calrify initital associations between specific genotypes and physical functioning.